PROVIDENCE — With the City Council mulling three plans to overhaul its membership and add at-large seats, the mayor has weighed in, throwing his support behind a proposal by Councilman Cliff Wood that would add at-large members at the expense of ward seats.

Three council members have submitted plans to add at-large council seats to the current ward structure. But the plans differ dramatically on how to accomplish that goal: one adds 2 at-large members, one adds 6, and a third creates 5 at-large positions at the expense of 5 ward seats. Mayor David N. Cicilline supports the third plan, maintaining the size of the council at 15, but opening 5 seats now elected by ward to citywide voting.

“This would encourage greater economic and cultural diversity among potential candidates for the at-large seats,” Cicilline wrote in a letter to the council.

That plan echoes changes recommended by the Charter Review Commission five years ago, and Cicilline urged the council to adopt them.

“The men and women of the Charter Review Commission invested a significant amount of time and effort into researching and developing a model that would work well in Providence, and I agree with their findings,” he wrote.

The Council Ordinance Committee had planned to take up the three proposals last night, but instead postponed action until two weeks from now, to allow for more research. Members said they plan to hold a public hearing after committee action to hear different points of view.

The original plan that touched off the debate was submitted by Councilman John J. Igliozzi, who represents Silver Lake. It would add 2 at-large members to the 15 council members, in an effort to maintain the current ward structure but add a voice of someone who could think about city-wide issues without having to answer to a particular section of the city.

Wood, who represents College Hill, submitted a second plan calling for the size of the council to remain the same at 15, but to redraw the ward map and replace 5 of the wards with at-large members elected by the entire city.

Wood has argued that adding more council members means costing the city more money. Each council member makes $18,000 a year.

Councilman Seth Yurdin, representing Fox Point, has put forth a third plan that would dramatically increase the size of the council to 21 members. It would keep the current 15 wards and add 6 at-large seats. The citywide seats would be elected by a method of proportional representation known as the single transferable vote to ensure that council members come from across the city and not solely from economically powerful areas like the East Side.

Yurdin’s proposal has the support of FairVote RI, but only if the proportional representation element is preserved. Otherwise, said Ari Savitzky, the director, the seats would simply lead to the city’s current elites expanding their power base.

“Winner-take-all at-large seats would be extremely expensive to campaign for and should favor those who have the resources to get elected,” Savitzky said. “Adding at-large seats without that component really skews the membership to wards that already have the power, whose voices are already being heard.”

The council membership seems in favor of some sort of change, but the feeling is not universal. Council President Peter S. Mancini is hesitant to add seats.

“If it’s not broken, don’t fix it,” Mancini said last night as the brief meeting concluded.

If the council does decide to adopt one of the three plans, or a hybrid version, any changes would have to be brought before the voters in the fall 2008 election.